1. Field of the Invention
The present invention relates in general to a chair in which the back upright portion is pivotable relative to the seat and, in particular, to a mechanism that provides a multi-position tilt limit adjustment for the back upright.
2. Description of Related Art Including Information Disclosed Under 37 C.F.R. xc2xa7xc2xa71.97 and 1.98
There are many chairs, particularly for use in offices, but not limited thereto, that have a back rest that is pivotable relative to the chair seat or the chair base to allow the user to select an angle at which the seat is most comfortable for him or her. One such tilt-limiting mechanism is discussed in U.S. Pat. No. 6,102,477 that has a complex mechanism for making the adjustment to the tilt angle of the bank rest.
Further, U.S. Pat. No. 4,408,800 discloses an office chair that has a pneumatic cylinder operated by a cam that can adjust the attitude of the back rest over a continuous range about a pivot. U.S. Pat. No. 4,509,793 discloses a chair in which the inclination of the back rest portion and the seat portion can be varied.
Finally, in German Patent No. 2,218,941, an adjustable chair back is disclosed in which a back rest holding bracket has an extension that projects toward the center under the seat. The back rest angle is determined by locking the end of the extension against a lock plate in the desired position. The extension has a plate with a series of indentations formed in an essentially arcuate manner that engages a spring-loaded arm to hold the back rest in one of a plurality of positions.
Each of these patented devices is complex and complicated. It would be desirable to have a simple, tilt-limiting mechanism that enables multi-tilt positions of the seat back to be achieved.
The present invention achieves the desired goal of providing a simple multi-tilt limiting mechanism for a chair back upright with the use of an engaging member affixed to the lower end of the back upright and a stop rotatively affixed to the bottom side of the seat plate. The stop has an outer edge with a changing radius for interacting with the engaging member on the chair back such that rotation of the stop enables the back upright to be tilted forward and backward with respect to the seat plate. A lever handle is coupled to the stop to enable the user to rotate this stop and select the tilt position of the back upright from a minimum tilt to a maximum tilt.
In the preferred embodiment, a stepped surface forms the outer edge of the stop for interfacing with the engaging member on the lower end of the back upright. The engaging member may be in the form of a protrusion. The stepped surface has multiple steps such that each step, when engaging the protrusion, enables the back upright to assume the selected tilt position.
The tilt limiting mechanism further comprises a locking means for holding a stop in a selected rotatable position to provide a fixed tilt position of the back upright. To provide the locking means, a series of indexing detents is formed in the top side of the rotatable stop with each detent representing a selected upright tilt position. A biased plunger is mounted between the bottom side of the seat plate and the rotatable stop such that the plunger is engageable with any selected indexing indent to hold the stop in a selected rotated position. The indexing detents have a concave shape and are adjacent to each other and the plunger is in the form of a spring-loaded plunger so as to enable it to freely move from one concave detent to another while compressing the spring. When the plunger is in any selected detent, the spring urging the plunger in that the detent causes the stop to hold the seat back upright tilt in the selected position.
Thus, it is the object of the present invention to provide a multi-position tilt-limiting mechanism for a chair back upright.
It is another object of the present invention to provide a protrusion affixed to the lower end of the back upright for engaging a stop rotatively affixed to the bottom side of the chair seat plate.
It is another object of the present invention to provide an outer edge on this stop having a changing radius for engaging the protrusion so that rotation of the stop enables the back upright to be tilted forward and backward with respect to the seat plate.
It is another object of the present invention to provide a lever handle coupled to the stop to enable a user to rotate the stop and select a tilted position of the back upright from a minimum tilt to a maximum tilt.
It is yet another object of the present invention to provide a stepped surface forming the outer edge of the stop for engaging a protrusion at the lower end of the seat back upright, the stepped surface having multiple steps such that each step position for engaging the protrusion enables the back upright to assume a given tilted position.
It is also another object of the present invention to form the locking means with a series of indexing indents on the top side of the rotatable stop wherein each detent represents a selected back upright tilt position. A spring-loaded plunger is mounted between the bottom side of the seat plate and the rotatable stop such that the plunger engages any selected one of the detents to hold the stop in a selected rotated position to limit the back upright position to the selected tilt position.
Thus, the invention relates to a multi-position tilt-limiting mechanism for a chair back upright, the back upright having an upper end and a lower end, the chair having a seat plate with a top side and a bottom side and the back upright being tiltable with respect to the seat plate. The tilt-limiting mechanism comprises a protrusion affixed to the lower end of the back upright, a rotatable stop being affixed to the bottom side of the seat plate and having an outer edge with a changing radius for engaging a protrusion such that rotation of the stop enables the back upright to be tilted forward and backward with respect to the seat plate. A lever handle is coupled to the stop to enable a user to rotate the stop and select a tilt position from a minimum tilt to a maximum tilt.
The present invention is part of complete new chair construction as disclosed and claimed in U.S. application Ser. No. 09/882,237, entitled xe2x80x9cErgonomic Chair,xe2x80x9d filed on even date herewith, the complete disclosure of which is incorporated by reference herein.